U.S. patent number 7,896,522 [Application Number 12/389,871] was granted by the patent office on 2011-03-01 for frontal illumination of a surface using led lighting.
This patent grant is currently assigned to Formetco, Inc.. Invention is credited to Todd R. Heller, Dewey T. Pitts.
United States Patent |
7,896,522 |
Heller , et al. |
March 1, 2011 |
Frontal illumination of a surface using LED lighting
Abstract
A plurality of lamp arrays (30A-30N) provide uniform lighting
across the copy area of a billboard sign. The arrays (30) are
arranged end-to-end horizontally along the length of the copy area.
Each array (30) comprises a plurality of LEDs (34A-34N) and a
plurality of lenses (36A-36M). The various lenses (36) direct and
focus the light from the LEDs (34) at the various parts of the copy
area so as to minimize dark and light spots. A "TOP" set of LEDs
preferably illuminates the top part of the copy area, a "MIDDLE"
set of LEDs preferably illuminates the middle of the copy area, and
"FILLER" LEDs preferably serve to illuminate the bottom of the copy
area. The lamp arrays are preferably mounted to a catwalk (14) at
the bottom of the billboard.
Inventors: |
Heller; Todd R. (Marietta,
GA), Pitts; Dewey T. (Marietta, GA) |
Assignee: |
Formetco, Inc. (Duluth,
GA)
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Family
ID: |
40672571 |
Appl.
No.: |
12/389,871 |
Filed: |
February 20, 2009 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20090290338 A1 |
Nov 26, 2009 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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61029952 |
Feb 20, 2008 |
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Current U.S.
Class: |
362/249.02;
362/249.01; 362/231; 362/235; 362/244; 40/541; 362/812 |
Current CPC
Class: |
G09F
13/02 (20130101); Y10S 362/812 (20130101); G09F
2013/222 (20130101) |
Current International
Class: |
G09F
13/02 (20060101) |
Field of
Search: |
;362/800,231,235,244,812,249.01,249.02 ;40/541-562 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0829844 |
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Sep 1997 |
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EP |
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0829844 |
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Sep 1997 |
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EP |
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0829844 |
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Mar 1998 |
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EP |
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2008015438 |
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Jan 2008 |
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JP |
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Other References
International Search Report and Written Opinion
(PCT/US2009/034681)--entire document. cited by other .
Automated translation of Publication EP0829844, Nov. 3, 1999,
Germany. cited by other.
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Primary Examiner: Ton; Anabel M
Attorney, Agent or Firm: Warner; Charles L. Bryan Cave
LLP
Parent Case Text
PRIORITY CLAIM
This application claims the priority of U.S. Provisional Patent
Application 61/029,952 filed on Feb. 20, 2008, entitled "Frontal
Illumination Of A Surface Using Led Lighting" by Todd R. Heller and
Dewey T. Pitts. The entirety of the above provisional application
is hereby incorporated herein by reference.
Claims
The invention claimed is:
1. An apparatus for illuminating substantially all of a desired
surface, the desired surface having an upper area, a middle area,
and a bottom area, the apparatus comprising: a plurality of light
arrays, the light arrays being arranged end-to-end and generally
parallel to the surface, each light array comprising: a housing; a
first light emitting diode (LED), with an associated lens, to
primarily illuminate a portion of the upper area of said surface
with a first predetermined pattern, said first LEDs of said light
arrays illuminating substantially all of the upper area; a second
LED, with an associated lens, to primarily illuminate a portion of
the middle area of said surface with a second predetermined
pattern, the second predetermined pattern being different from the
first predetermined pattern, said second LEDs of said light arrays
illuminating substantially all of the middle area; and a third LED
to illuminate at least a portion of the bottom area of said
surface, said third LEDs of said light arrays illuminating
substantially all of the bottom area.
2. The apparatus of claim 1 wherein the surface is the copy area on
a billboard, and the billboard has a catwalk extending from the
front thereof, and wherein the light arrays are directly mounted
to, and are in close proximity to, either the catwalk or a kickrail
of the catwalk.
3. The apparatus of claim 1 wherein the surface is the copy area on
a billboard, and the billboard has a catwalk extending from the
front thereof, and further comprising at least one mounting bracket
for securing a lighting array to, and in close proximity to, either
the catwalk or a kickrail of the catwalk.
4. A method for illuminating substantially all of a desired
surface, the desired surface having a higher part, a central part,
and a lower part, the method comprising: generating light by
providing operating power to a plurality of light arrays, the light
arrays being arranged in end-to-end and generally parallel to the
surface, each light array comprising a plurality of light emitting
diodes (LEDs) which are generally evenly distributed within the
light array along a line generally parallel to the surface, the
light from each light source being oriented generally toward the
surface; and focusing the light from a first set of said LEDs onto
the higher part of the surface, the light from each LED being
independently focused in a first predetermined shape, the light
from the first set of LEDs illuminating substantially all of the
higher part; focusing the light from a second set of said LEDs onto
the central part of the surface, the light from each LED being
independently focused in a second predetermined shape, said second
predetermined shape being different from said first predetermined
shape, the light from the second set of LEDs illuminating
substantially all of the central part; and directing the light from
a third set of said LEDs onto at least a lower part of the surface,
the light from the third set of LEDs illuminating substantially all
of the lower part.
5. A light array for illuminating substantially all of a desired
surface, comprising: a housing; a plurality of light emitting
diodes (LEDs) contained within the housing and being generally
evenly distributed within the housing along a line generally
parallel to the surface, each LED of the plurality of LEDs being
oriented generally toward the desired surface; and a plurality of
lenses contained with the housing, the plurality of lenses covering
at least a majority of the LEDs, each lens of the plurality of
lenses being associated with an LED of the plurality of LEDs and
focusing the light from the associated LED toward a predetermined
portion of the desired surface; a first set of said lenses focusing
light primarily onto a first part of the desired surface so that
substantially all of the first part is illuminated; a second set of
said lenses focusing light primarily onto a second part of the
desired surface so that substantially all of the second part is
illuminated; and at least some of the LEDs directing light at least
to a third part of the desired surface so that substantially all of
the third part is illuminated, the LEDs directing light at least to
a third part not being associated with either the first set of
lenses of or the second set of lenses.
6. The light array of claim 5 wherein at least some of the LEDs
directing light to the third part of the surface also direct light
to the first part of the surface.
7. The light array of claim 5 wherein at least some of the LEDs
directing light to the third part of the surface also direct light
to the second part of the surface.
8. The apparatus of claim 1 wherein said third LEDs also illuminate
a portion of the middle area.
9. The apparatus of claim 1 wherein said third LEDs also illuminate
a portion of the upper area.
10. The method of claim 4 wherein a first predetermined shape on
said higher part of the surface overlaps an adjacent first
predetermined shape on said higher part of the surface.
11. The method of claim 4 wherein a second predetermined shape on
said central part of the surface overlaps an adjacent second
predetermined shape on said central part of the surface.
12. The method of claim 4 wherein a first predetermined shape on
said higher part of the surface overlaps an adjacent second
predetermined shape on said central part of the surface.
13. The apparatus of claim 1 wherein the apparatus illuminates a
billboard as the desired surface.
14. The light array of claim 5 wherein the light array illuminates
a billboard as the desired surface.
15. The method of claim 4 wherein the light from each light source
is oriented generally toward a billboard as the desired surface.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to lighting of billboards,
signs, buildings, and other structures and, more particularly,
relates to front illumination of surfaces using light emitting
diodes (LEDs).
2. Description of the Related Art
Historically, light fixtures providing front illumination of large
advertising billboards have utilized various types of illumination
sources, including electro-florescent tubes and flood lights
(incandescent, high energy discharge, projection lamps). The
illumination source is enclosed in a fixture which is mounted on an
extended arm, and the extended arm positions the illumination
source, also referred to as a light source, far enough away from
the billboard face to illuminate the image area (or "copy area")
for viewing in low light conditions. Typically, because of the
beamwidth limitations of the light source, two or more light
fixtures are needed to illuminate the copy area. The number of
light fixtures needed thus depends upon the height and width of the
copy area and the beamwidth of the light source. Also, in order to
provide the desired dispersion of the light from the light sources,
and to provide for relatively even illumination from top to bottom
of the copy area, the light sources have to be set back from the
billboard face, typically 6 to 8 feet. The fixture mounting system
is typically attached to the billboard support structure, either at
or near the top of, the bottom of, or both the top and the bottom
of, the billboard face. The fixture mounting system therefore
typically extends the light fixture in front of the billboard face.
The mounting device for each fixture typically consists of a metal
tube, arm, or conduit which is mounted to the billboard structure,
and which extends out approximately 6 to 8 feet, the light source
typically being attached at or near the end of the fixture.
A larger number of light sources provides for more even
illumination of the copy area, but generally results in higher
costs, more physical structures, higher wind loading, and more
maintenance issues. Conversely, a lower number of light sources
results in lower cost, fewer physical structures, lower wind
loading, and fewer maintenance issues, but increases the likelihood
that there will be noticeable and undesirable differences between
better lit (lighter) areas and more poorly lit (darker) areas. As a
compromise between these opposing goals and choices, a typical
installation may use only a few light sources, spaced at intervals
of 8 to 12 feet. To compensate for using a small number of light
sources, the light sources are generally wide-angle light sources,
so that the fields of illumination provided by the light sources
overlap somewhat, thereby reducing the contrast between the
differently-illuminated areas. The use of wide angle light sources,
however, brings on other problems such as, but not limited to, (1)
inefficiency because the use of wide-angle light sources causes a
substantial amount of the light emitted to be spread outside the
borders of the copy area; (2) undesired heat generation because
more light output, and therefore more energy, is required so that
the light which strikes the copy area is of sufficient intensity to
properly illuminate the copy area; and (3) light pollution problems
because the light which does not strike the copy area contributes
to night sky light pollution. Night sky pollution has become such a
severe problem in many large cities that only the brightest stars
are visible at night.
Simply replacing the current light sources with LED light sources
would seem to be a solution but, in reality, is not a solution
because of several problems: (1) a large number of LEDs is required
to provide the desired illumination, (2) the optics and lensing
required to illuminate the copy area sufficiently is very complex,
(3) the heat generated by a large number of LEDs in close proximity
or clustered together causes the LEDs to quickly overheat and fail,
and (4) cost, windloading, esthetic, maintenance, and other
considerations. Thus, neither simply replacing conventional light
sources with clustered LEDs, nor adding more projecting fixtures
with fewer LEDs in a fixture, are viable options.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is an illustration of a billboard and shows the billboard
face, the catwalk, and one possible LED lamp location.
FIG. 2 is an illustration of a billboard and shows the billboard
face, the catwalk, and another possible LED lamp location.
FIG. 3 is an illustration of a billboard and shows the billboard
face, the catwalk, another possible LED lamp location, and the
preferred light dispersion characteristic.
FIG. 4 is an illustration of one embodiment of a lamp array.
FIG. 5 is an illustration of another embodiment of a lamp
array.
FIG. 6 is a side elevation cutaway view of an embodiment of a lamp
array, and shows a typical position for the power supply and an
individual LED cell.
FIGS. 7 and 8 are photographs of an embodiment of a lamp array and
show LED cells, both with and without optical lenses.
FIGS. 9 and 10 are photographs of an embodiment of a lamp array and
show the protective cover in place.
FIGS. 11A-11E are illustration of various LED cell configurations
and various optical lensing arrangements.
FIG. 12 is a photograph showing the light distribution provided by
the LED lamp array of one embodiment.
FIG. 13 is a photograph illustrating one method of connecting lamp
arrays.
DETAILED DESCRIPTION
FIGS. 1-3 illustrate embodiments of various billboard installations
and some location possibilities for LED lamp arrays. FIG. 1 is an
illustration of one embodiment of a billboard 10 and shows the
billboard face 12, the catwalk 14, and one possible location 16 for
lamp arrays 30A-30N. FIG. 2 is an illustration another embodiment
of a billboard 10, and shows the billboard face 12, the catwalk 14,
and another possible location 16 for the lamp arrays 30. FIG. 3 is
an illustration of another embodiment of a billboard 10 and shows
the billboard face 12, the catwalk 14, another possible location 16
for the lamp arrays 30, and the preferred light dispersion
characteristic 20.
The front illuminated sign has a plurality of LED lamp arrays
30A-30N, also referred to herein as light fixtures, preferably
mounted to the service access catwalk 14 kickrail, and parallel to
the advertising sign face 12. An adjustable mounting bracket 15
accommodates various relationships between the advertising sign
face 12 and the location of the service access catwalk 14 toe and
kick rails 14A, 14B, such as differences in the locations of the
catwalk kickrails in relationship to the sign face. Each LED light
fixture is preferably long and rectangular in shape, and has either
a single row or multiple rows of LED lamps. The fixtures are
mounted on the service access catwalk kickrail, running
horizontally along most of the length of the kickrail. Optical lens
on the LED lamps selectively and purposefully distribute light
vertically and horizontally across the copy area. Preferably,
different lens with different light distribution patterns are used
for the various LEDs. Even spacing of LED lamps, placed
horizontally along the catwalk kickrail, and directed towards the
face of the billboard, results in consistent illumination of the
copy area.
The illustrated embodiments provide a visually appealing method of
illuminating the copy area of a billboard face from the front.
There are no protruding light fixtures at the top or the bottom of
the billboard. There is no need to obtain extended property line
set back permission to accommodate the protruding light fixtures
because the LED lights preferably occupy the same latitudinal space
as the catwalks present on most billboards. Such catwalks are
typically present to provide access for installation and changing
of the advertising message, changing light bulbs, general servicing
of the billboard, etc. More uniform horizontal illumination can be
obtained as a result of evenly spacing LED fixtures along the
catwalk kickrail, as opposed to adding and positioning protruding
light fixtures. In addition to providing for more even
illumination, evenly spacing LED fixtures along the catwalk
kickrail eliminates the need for large clusters of LEDs. LED
fixtures, especially those intended to be direct replacements for
conventional light fixtures typically have large clusters of LEDs,
which generate excessive heat build-up, resulting in premature LED
failure. The use of the evenly spaced horizontal LED fixtures
described herein provides for less power consumption, longer
operating lifetimes, cooler operating temperatures, and
considerably smaller fixtures than flood lights,
electro-fluorescent tubes, or clustered LED fixtures.
The illustrated embodiments provide for front illumination of
advertising billboards and other vertical surfaces by using a
plurality of horizontally oriented, preferably evenly spaced, LED
light fixtures which are mounted to the service access catwalk
kickrail parallel to the billboard or sign face.
The illustrated embodiments also provide for an efficient layout of
the LEDs, which simplifies cooling and efficiently distributes
light in order to illuminate the copy area over a long horizontal
distance. The LED fixtures are preferably evenly-spaced
horizontally along the front of the sign face, and are preferably
mounted in one, two, or three rows to avoid the build-up of heat,
which buildup can reduce LED longevity. A buildup of heat is
typical of spotlight-type fixtures, including cluster LED
fixtures.
In addition, lamp arrays 30A-30N may be stacked so as to achieve
more luminosity, and the rows may be offset from one another so as
to achieve a more uniform illumination across the copy area.
FIGS. 4-6 illustrate embodiments of various LED lamp array
configurations. FIG. 4 is an illustration of one embodiment of a
lamp array 30 and shows a housing 32, a plurality of LEDs 34A-34N
and a plurality of lens elements 36A-36M, where M is less than or
equal to N, and, preferably, a cover 38 to protect the LEDs 34 and
lens 36 from the environment.
FIG. 5 is an illustration of another embodiment of a lamp array 30
and shows a housing 32 and, preferably, a cover 38. The LEDs 34 and
lens 36 are present but are not shown in this view.
FIG. 6 is a side elevation cutaway view of the embodiment of the
lamp array 30, such as the embodiment of FIG. 4, and shows the
housing 32, a typical position for the power supply 40, and one LED
34/lens 36 combination.
FIGS. 7-10 are photographs of exemplary lamp arrays 30. FIG. 7
shows an exemplary embodiment of a lamp array 30 with an LED cell
34 covered by an optical lens 36. FIG. 8 shows an exemplary
embodiment of a lamp array 30 with an LED cell 34 which is not
covered by an optical lens.
FIGS. 9 and 10 show an exemplary embodiment of a lamp arrays 30
from two different perspectives, and show the protective cover 38
in place.
As shown in FIGS. 1-3, the lamp arrays 30A-30N are lined up, end to
end, at the desired position with respect to the catwalk 14, some
but not all of which positions are shown. As can be seen, all LEDs
34 of the lamp arrays 30 preferably lie along the same line or
axis, and are generally evenly spaced along the length of the
catwalk 14. The lamp arrays 30 are preferably mounted just outside
the catwalk area 14, which provides for ease of maintenance, such
as replacing a cracked protective cover 38.
FIGS. 11A-11E illustrate some exemplary LED cell 34 configurations
for a lamp array 30. The LEDs 34 are spaced approximately 4 inches
apart, which distance is preferred, but is not critical. The
spacing is based on a tradeoff between, for example, the acceptable
difference in the illumination levels in adjacent or even
non-adjacent sections of the copy area, the minimum amount of
lighting required, and the cost tradeoffs between higher power, but
fewer, LEDs, and fewer lens, versus lesser power, but more, LEDs,
and more lens, etc.
FIG. 11A illustrates an embodiment wherein lenses 36 are used on
all of the LEDs 34. The various lenses 36 may be the same type or
may be different types depending upon the uniformity of
illumination desired or acceptable, color(s) desired, cost
considerations, etc.
It will be appreciated that light from a light source spreads as
the light gets farther away from the light source, so an area at
one distance will receive a different amount of light than the same
size area at a different distance. Further, it will be appreciated
that a surface which receives light from a light source shining
directly at the surface will have a higher level of illumination
per area of surface than if that same surface were turned at an
angle to the light source. To compensate for these effects, for
example, when the LED arrays are mounted toward the bottom of the
billboard face such as on the catwalk, then more of the light is
directed toward the upper portion of the copy area, because the
upper portion is farther away from the LED arrays than the bottom
portion and is at a greater angle with respect to the LED arrays
than the bottom portion.
FIG. 11B shows an embodiment wherein different lenses 36 are used
on some of the LEDs 34 and, preferably, no lenses are used on other
LEDs 34. The designations "TOP", "MIDDLE", and "FILLER" indicate
the general vertical position on the copy area where the light from
that particular LED 34 strikes the copy area. For example, for a
billboard which has a copy area height of approximately 14 feet, a
TOP area is preferably, but not necessarily, an oval area,
approximately 2.5 feet high by 5 feet wide, the center of this TOP
area being approximately 1.25 feet from the top edge of the copy
area. A MIDDLE area is preferably, but not necessarily, a circular
area, approximately 5 feet high by 5 feet wide, the center of this
MIDDLE area being approximately 7 feet from the top edge of the
copy area. Although the TOP and MIDDLE areas could overlap, an
overlap is not necessary so, in this embodiment, these areas do not
overlap. It will be appreciated that the illumination outside of an
area does not abruptly fall to zero outside of the area, but tapers
off. Thus, a TOP position LED will provide some illumination
outside of the TOP area, and a MIDDLE position LED will provide
some illumination outside of the MIDDLE area. These outside-area
illuminations therefore combine and enhance the uniformity of the
illumination.
A "FILLER" (or "BOTTOM") area is preferably, but not necessarily,
approximately the bottom half of the copy area, such as from the
bottom edge of the copy area to approximately 9 feet from the
bottom edge of the copy area. The FILLER area may be determined by
focusing the light output from a FILLER LED, such as by using a
lens, or may be determined by the characteristics of the particular
LED device used. Although the MIDDLE and FILLER areas could
overlap, an overlap is not necessary so, in this embodiment, these
areas do not overlap. It will be appreciated, as mentioned above,
that the illumination outside of an area does not abruptly fall to
zero outside of the area, but tapers off.
The TOP and MIDDLE areas are obtained by the use of focusing lenses
and, in one embodiment, the focusing lens for a TOP LED has a
beamwidth of 23 degrees by 50 degrees, and the focusing lens for a
MIDDLE LED has a beamwidth of 45 degrees. The FILLER LED
preferably, but not necessarily, does not use a focusing lens. As
used herein, the term "focus" is not limited to the narrowing of a
beam of light from an LED but also includes broadening of a beam
and adjusting the pattern of a beam.
In operation of a preferred embodiment, the TOP LEDs will
illuminate the uppermost portions of the copy area. Preferably, the
illumination footprints provided by the TOP LEDs in the same lamp
array will overlap, and the illumination footprints provided by the
TOP LEDs in adjacent arrays will overlap. The MIDDLE LEDs will
illuminate the middle portions of the copy area. Also, preferably,
the illumination footprints provided by the MIDDLE LEDs in the same
lamp array will overlap, the illumination footprints provided by
the MIDDLE LEDs in adjacent arrays will overlap. The FILLER LEDs
preferably illuminate at least the bottom portion of the copy area.
Preferably, the illumination footprints provided by the FILLER LEDs
in the same lamp array will overlap, and the illumination
footprints provided by the FILLER LEDs in adjacent arrays will
overlap. The overlap, or near overlap, between different footprints
serves to make the illumination more uniform across the billboard
and to reduce contrast between adjacent areas. Too little overlap
can cause darker areas to appear, while too much overlap can cause
brighter areas to appear, as well as increasing the cost of
operation.
FIG. 11C is an illustration of one LED cell configuration, such as
might be used in FIGS. 11A and 11B, but without the lenses.
FIGS. 11D and 11E show two alternative LED cell configurations
wherein the LEDs are grouped. One situation in which these
configurations may be used is, for example, when additional
lighting is required so that the billboard face can be seen from a
greater distance or in conditions other than near or total
darkness. Another situation in which they may be used is, for
example, to provide different colors or color effects. For example,
all LEDs in a group may have the same color (but preferably
different lens), and different groups may have different colors. As
another example, the LEDs in a group may have different colors (and
preferably similar or identical lens), and different groups may
have lens with different characteristics.
In one embodiment, the LEDs are type Xlamp.TM. XR-E manufactured by
Cree.TM. of Durham, N.C., and have an output of 100 Lumens at 350
milliamps (ma). These LEDs are rated at a current input of up to
1000 ma and, in one embodiment, the current input is 950 ma, which
provides a light output of 180 Lumens. In another embodiment, the
LEDs are type XLamp 7090 XR, also manufactured by Cree.
In one embodiment, such as when the above-mentioned Cree LEDs are
used, the lens is an "FC Lens", sold by Fraen.TM. Corporation,
Reading, Mass. In another embodiment, the lens is a "CRS Square
Lenses", for CREE XR-E LEDs, sold by Marubeni America.TM.
Corporation, Santa Clara, Calif. In one embodiment, the lens used
for the "TOP" position LEDs is a type CRS-O manufactured by Ledil
Oy.TM., Salo, Finland, which has a vertical beamwidth of 28 degrees
and a horizontal beamwidth of 12 degrees, and the lens used for the
"MIDDLE" position LEDs is a type FC-W2-XR79-HRF manufactured by
Fraen Corporation, and has a beamwidth (horizontal and vertical) of
41 degrees.
In another embodiment, rather than there being a single row of LEDs
in a lamp array 30, there are two or more rows of LEDs in an array.
The LEDs in the different rows may be in a vertical column, or they
may be offset, if desired, so as to further and more evenly
distribute the light shining on the copy area. For example, FIG.
11D shows a lamp array which has two rows of LEDs in a vertical
column, and FIG. 11E shows a lamp array which may be considered to
have three rows, the center row being offset horizontally from the
other two rows. Other embodiments are also possible such as, for
example, where the top row in FIG. 11D is offset, with respect to
the bottom row, by one-half of the distance between the elements in
the bottom row.
Although the embodiments are depicted on billboards which have
catwalks, the LED arrays can also be used on billboards which do
not have catwalks. One could use, for example, a plurality of
mounting arms to support the arrays. One could also, for example,
provide a railing, set out from the bottom of the billboard, and
held in place by a plurality of mounting arms, and fasten the
arrays to the railing. Also, although the embodiments shown have
the LED arrays mounted toward the bottom of the billboard, pointing
generally upwardly, the LED arrays can, instead, be mounted toward
the top of the billboard, and generally pointing downward. Top
mounting of the arrays may be accomplished, for example, by a
plurality of mounting arms as mentioned above, or by a railing set
out from the top billboard and held in place by a plurality of
mounting arms. Also, if there are two billboards which are stacked,
then the arrays could be mounted to the catwalk of the upper
billboard and, in this case, the catwalk on the upper billboard may
serve for mounting of the light arrays for both the upper billboard
and the lower billboard. In addition, if exceptional uniformity of
illumination is desired, or if exceptional luminance is desired,
then two sets of LED arrays could be used, one mounted toward the
bottom of the billboard, pointing generally upwardly, and the other
mounted toward the top of the billboard, and generally pointing
downward.
For convenience of discussion below, it is assumed that the copy
area has a size of 12 feet.times.24 feet. Thus, the copy area could
be considered to be a 12 foot by 24 foot matrix of light surfaces.
Also for convenience, Table I and Table II have both been broken
into two table segments, with the top segment of the table
representing the left one-half of the copy area, and the bottom
part representing the right one-half of the copy area.
Table I shows the illumination across a 12 foot by 24 foot panel,
which is illuminated by a typical four-projection arm and light
source array. The total power provided to the four High Intensity
Discharge lamps (HID) is 432 watts (3.6 amps at 120 VAC), and the
four arrays produce an illumination of 42,000 Lumens. The panel is
divided into 1 foot squares, but measurements were not taken on the
leftmost, rightmost, topmost, or bottommost squares. Accordingly,
measurements were conducted on 220 (10.times.22) squares. The
numbers show the illumination in foot-candles for each square and
are actual measurements, except that the values for squares A6-A22,
B6-B22, and C16-C22 are estimates. From this, it can be seen that
the total copy area illumination is 11152 footcandles, the average
illumination is 50.60 footcandles, and the low and high
illuminations are 16 and 124 footcandles, respectively. As the
arrays produce 42000 lumens, and only 11152 lumens strike the
board, this means that up to 30848 lumens are not used,
contributing nothing to the illumination of the copy area, but
contributing to night sky pollution. In other words, only about
26.55% of the illumination strikes the copy area, and the other
73.45% is effectively wasted.
Table II similarly shows the illumination across a 12 foot by 24
foot panel, which is illuminated by an embodiment using LEDs. The
total power provided to the LEDs is 240 watts (2.0 amps at 120
VAC), and the LEDs produce an illumination of 13,500 Lumens. The
numbers show the illumination in foot-candles for each square and
are actual measurements, except that the values for squares A6-A22,
B6-B22, and C6-C22 are estimates. From this, it can be seen that
the total copy area illumination is 10747.6 footcandles, the
average illumination is 48.85 footcandles, and the low and high
illuminations are 12.6 and 99 footcandles, respectively. As the
arrays produce 13500 lumens, and 10747.6 lumens strike the board,
this means that only 2752.4 lumens are not used. In other words,
about 79.61% of the illumination strikes the desired areas of the
copy area, and only 20.39% is wasted.
Therefore, the efficiency of the LED fixture, as compared to the
High Density fixture, has been increased almost three-fold, from
26.55% to 79.61%. Further, the power consumption has been reduced
by over 40% but the total light striking the copy area has
decreased by less than 4%.
FIG. 12 is a photograph showing the light distribution provided by
the LED lamp array of one embodiment.
FIG. 13 is a photograph illustrating one method of connecting lamp
arrays 30 in an end-to-end configuration. The lamp arrays 30 have
end caps 40, and are held together by mounting hardware 42, such
as, but not limited to, a bolt and a nut. The method of connecting
the lamp arrays 30 is not critical and other techniques may be
used.
TABLE-US-00001 TABLE I HID LIGHTING 1 2 3 4 5 6 7 8 9 10 11 A 18 21
23 26 28 28 29 32 32 31 30 B 19 24 28 31 36 37 36 39 41 40 38 C 20
26 33 39 43 46 46 48 50 50 49 D 19 25 36 46 51 57 58 57 60 61 58 E
19 26 35 45 60 67 72 69 69 70 67 F 17 24 33 49 62 73 78 82 80 80 77
G 16 20 29 41 61 72 79 85 93 100 103 H 17 21 27 35 48 66 73 83 101
114 124 I 19 22 29 35 44 54 69 82 98 107 109 J 18 23 28 38 41 49 47
60 82 95 86 12 13 14 15 16 17 18 19 20 21 22 A 30 31 32 32 29 28 28
26 23 21 18 B 38 40 41 39 36 37 36 31 28 24 19 C 49 50 50 48 46 46
43 39 33 25 20 D 58 61 60 57 58 57 51 46 36 25 19 E 67 70 69 69 72
67 60 45 35 26 19 F 77 80 80 82 78 73 62 49 33 24 17 G 103 100 96
85 79 72 61 41 29 20 16 H 124 114 101 83 73 66 48 35 27 21 17 I 109
107 98 82 69 54 44 35 29 22 19 J 86 86 95 82 60 47 49 41 38 26
23
TABLE-US-00002 TABLE II LED LIGHTING 1 2 3 4 5 6 7 8 9 10 11 A 16.5
18 19 25 31.6 31.6 31.6 31.6 31.6 31.6 31.6 B 19.9 21.5 24.3 30
39.5 39.5 39.5 39.5 39.5 39.5 39.5 C 25.9 29.9 32.4 39.5 49 49 49
49 49 49 49 D 33.8 39.3 44.6 51.8 60.7 62 66 60 50 57 64 E 41.7
50.7 53.8 57 71.7 71 71 62 53 65 76 F 39.1 50.1 59.2 65.6 74.5 80.1
79 65 60 76 83 G 27.7 38 50 62 70 82 84 70 66 83 92 H 21.3 33.8
43.6 53.1 63.2 77 84 67 63.5 87.3 94.1 I 17.6 30.3 41.8 45.8 47.6
54 57 80 48 69 68 J 13 20 26 27 27 29 29 27 29 34 37 12 13 14 15 16
17 18 19 20 21 22 A 31.6 31.6 31.6 31.6 31.6 31.6 31.6 25 19 18
16.5 B 39.5 39.5 39.5 39.5 39.5 39.5 39.5 30 24.3 21.5 19.9 C 49 49
49 49 49 49 49 39.5 32.4 29.9 25.9 D 63 55 57 64 62 53 46 45 44 34
16.5 E 72 61 65 68 66 58 51 53 50 40 17 F 78 65 71.2 74 73 64 53 56
57 41 18 G 87 71 80 81 80 72 65 63 64 49 17.8 H 99 70.1 82 84 78
69.9 66.8 65.5 65.1 47.9 18.6 I 71 58 59 60 61 57 58 56 54 38 16 J
35 32 31 34 34 34 35 37 34 25 12.6
It will be appreciated that the individual LEDs may be individually
focused onto the copy area at the desired location and with the
desired beamwidth. It will also be appreciated that if top mounting
of the light array is desired, then some mounting mechanism must be
provided to replace the catwalk used for bottom mounting of the
light array. Even in such a case, however, the light array will
still be closer to the copy area than in conventional technology,
and there will not be the long projection arms used by conventional
technology.
The housing may be secured to the catwalk, or to another available
mounting surface, by any convenient technology, such as, but not
limited to, bolts, clamps, straps, and welding. Also, although not
shown, it will be appreciated that electrical power must be
provided to the light arrays in some manner, such as by
conventional wiring.
In addition to billboards, the LED arrays may be used to illuminate
the side of a building, such as for esthetic purposes. The LED
arrays can be, if desired, mounted using supports extending from
the sides of the building, or may be mounted on, for example,
existing ledges of the building. The LED arrays may also be used to
light highway and roadway signs, from above or from below, or
both.
Various advantages and benefits result from the above. Although
each embodiment provides at least one advantage or benefit, there
is no requirement that any embodiment must provide all benefits, as
tradeoffs are to be expected. Therefore, it is expected that one of
ordinary skill in the art can and will choose among the various
characteristics and features of the various embodiments to achieve
the desired illumination result.
* * * * *